Usage
- Amitriptyline + Methylcobalamin is prescribed for the management of neuropathic pain (nerve pain), such as diabetic neuropathy, trigeminal neuralgia, and postherpetic neuralgia. It is also used for other types of chronic pain, such as fibromyalgia. Amitriptyline is used to treat depression and its component can help with anxiety, insomnia, and chronic pain conditions. Methylcobalamin improves nerve cell health and supports nerve signaling.
- Pharmacological Classification: Amitriptyline is a tricyclic antidepressant (TCA), and Methylcobalamin is a vitamin B12 analog. Therefore, this combination acts as an analgesic, antidepressant, and neurotrophic agent.
- Mechanism of Action: Amitriptyline inhibits the reuptake of serotonin and norepinephrine, increasing their levels in the synaptic cleft. Methylcobalamin plays a vital role in nerve cell maintenance and myelination. The synergistic action provides pain relief and improves nerve function.
Alternate Names
- No internationally recognized alternate names exist for the combination itself.
- Brand Names: Amnurite, Nervijen-P
How It Works
- Pharmacodynamics: Amitriptyline exerts its analgesic effect by modulating pain pathways in the central nervous system. Methylcobalamin promotes nerve regeneration and improves nerve conduction velocity.
- Pharmacokinetics:
- Absorption: Amitriptyline is well-absorbed orally. Methylcobalamin is also well-absorbed.
- Metabolism: Amitriptyline is extensively metabolized in the liver, primarily by CYP2D6 and CYP2C19. Methylcobalamin is converted to its active coenzyme forms.
- Elimination: Amitriptyline is primarily excreted in urine as metabolites. Methylcobalamin is excreted in both urine and bile.
- Mode of Action: Amitriptyline binds to serotonin and norepinephrine reuptake transporters, inhibiting their function. Methylcobalamin acts as a coenzyme for methionine synthase and methylmalonyl-CoA mutase, which are essential for DNA synthesis and myelin formation.
- Receptor binding: Amitriptyline blocks serotonin and norepinephrine transporters.
- Elimination Pathways: Primarily hepatic metabolism for amitriptyline, renal and biliary excretion for both.
Dosage
Standard Dosage
Adults:
- Initially, 25-50 mg orally at bedtime. The dosage may be gradually increased as needed and tolerated, up to a maximum of 150 mg/day.
- For neuropathic pain, the combination product containing 5 mg amitriptyline and 1500 mcg methylcobalamin is often prescribed once daily.
Children:
- Not typically recommended for children under 12 years old. Dosage for adolescents should be determined by a physician.
Special Cases:
- Elderly Patients: Start with a lower dose (10-25 mg/day) and titrate cautiously.
- Patients with Renal Impairment: Use with caution; dose adjustment may be needed.
- Patients with Hepatic Dysfunction: Contraindicated in severe liver disease. Use with caution in mild to moderate impairment; dose reduction may be necessary.
- Patients with Comorbid Conditions: Caution should be exercised in patients with cardiovascular disease, glaucoma, or urinary retention.
Clinical Use Cases
- The combination is not typically used in acute settings like intubation, surgical procedures, mechanical ventilation, ICU, or emergency situations. It is primarily intended for chronic pain management.
Dosage Adjustments
- Dosage adjustments should be made based on individual patient response and tolerability. Consider renal/hepatic function, and comorbid conditions.
Side Effects
Common Side Effects:
- Drowsiness, dizziness, dry mouth, constipation, blurred vision, urinary retention, weight gain.
Rare but Serious Side Effects:
- Cardiac arrhythmias, seizures, serotonin syndrome, neuroleptic malignant syndrome, allergic reactions.
Long-Term Effects:
- Potential for tolerance and dependence with prolonged use of amitriptyline.
Adverse Drug Reactions (ADR):
- Any signs of cardiac arrhythmias, serotonin syndrome, or neuroleptic malignant syndrome require immediate medical attention.
Contraindications
- Hypersensitivity to either component.
- Recent myocardial infarction.
- Glaucoma.
- Urinary retention.
- Concomitant use of MAO inhibitors.
Drug Interactions
- MAO inhibitors, other antidepressants, anticholinergics, CNS depressants, CYP2D6 inhibitors or inducers, alcohol.
Pregnancy and Breastfeeding
- Amitriptyline is generally avoided during pregnancy, especially in the first and third trimesters, unless the benefits outweigh the risks. Consult a physician regarding its use during breastfeeding.
Drug Profile Summary
- Mechanism of Action: Amitriptyline: TCA inhibiting serotonin and norepinephrine reuptake. Methylcobalamin: Vitamin B12 analog promoting nerve health.
- Side Effects: Drowsiness, dizziness, dry mouth, constipation. Serious: cardiac arrhythmias, seizures.
- Contraindications: Hypersensitivity, recent MI, glaucoma, urinary retention, concurrent MAOIs.
- Drug Interactions: MAOIs, other antidepressants, anticholinergics, CNS depressants.
- Pregnancy & Breastfeeding: Consult physician.
- Dosage: Adults: Start 25-50 mg/day, up to 150 mg/day. Children: Not recommended under 12.
- Monitoring Parameters: Cardiac function, mental status.
Popular Combinations
- Sometimes used in combination with other pain medications like gabapentin or pregabalin.
Precautions
- Monitor for cardiac effects and mental status changes.
- Caution in elderly, patients with renal/hepatic impairment, or comorbid conditions.
- Avoid alcohol.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Amitriptyline + Methylcobalamin?
A: Adults: Initially 25-50mg at bedtime, titrated up to 150 mg/day. Children: Not recommended under 12. Elderly: Lower initial dose.
Q2: What are the common side effects?
A: Drowsiness, dizziness, dry mouth, constipation, blurred vision.
Q3: How does this combination treat neuropathic pain?
A: Amitriptyline modulates pain pathways, and methylcobalamin supports nerve regeneration.
Q4: Can pregnant or breastfeeding women take this medication?
A: Consult a physician. Generally avoided in pregnancy. Use with caution during breastfeeding.
Q5: What are the serious side effects to watch out for?
A: Cardiac arrhythmias, seizures, serotonin syndrome.
Q6: What medications should be avoided while taking this combination?
A: MAO inhibitors, other antidepressants, alcohol, and certain other medications metabolized by the liver.
Q7: Are there any dietary restrictions?
A: Alcohol should be avoided.
Q8: How long does it take to see improvement in pain?
A: Several weeks of consistent treatment may be necessary for noticeable pain relief.
Q9: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember, unless it is almost time for the next dose. Do not double the dose.
Q10: Can this combination be used for other types of pain?
A: While primarily used for neuropathic pain, it can be used for other chronic pain conditions like fibromyalgia, but under strict medical supervision.
